Two women, A and B working separately can mow a field in 8 : GMAT Problem Solving (PS)
Check GMAT Club Decision Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

 It is currently 19 Jan 2017, 18:43

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# Two women, A and B working separately can mow a field in 8

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:

### Hide Tags

Manager
Joined: 24 Jan 2010
Posts: 164
Location: India
Schools: ISB
Followers: 2

Kudos [?]: 53 [1] , given: 14

Two women, A and B working separately can mow a field in 8 [#permalink]

### Show Tags

28 Jun 2010, 08:01
1
KUDOS
7
This post was
BOOKMARKED
00:00

Difficulty:

65% (hard)

Question Stats:

51% (02:13) correct 49% (02:08) wrong based on 63 sessions

### HideShow timer Statistics

Two women, A and B working separately can mow a field in 8 and 12 hrs respectively. If they work together in stretches on 1 hr alternately, A beginning at 9:00 AM, when will the mowing be finished?

Can anybody plz explain the best way to solve such problems?
[Reveal] Spoiler: OA

_________________

_________________
If you like my post, consider giving me a kudos. THANKS!

Math Expert
Joined: 02 Sep 2009
Posts: 36567
Followers: 7081

Kudos [?]: 93212 [5] , given: 10553

Re: Working Alternately [#permalink]

### Show Tags

28 Jun 2010, 08:34
5
KUDOS
Expert's post
5
This post was
BOOKMARKED
Two women, A and B working separately can mow a field in 8 and 12 hrs respectively. If they work together in stretches on 1 hr alternately, A beginning at 9:00 AM, when will the mowing be finished?

Can anybody plz explain the best way to solve such problems?

In 1 hour A does $$\frac{1}{8}=\frac{3}{24}$$th of the whole job and B $$\frac{1}{12}=\frac{2}{24}$$th of the whole job (common denimnator makes the following calculations easier). So in 2 hours they do $$\frac{3}{24}+\frac{2}{24}=\frac{5}{24}$$th of the whole job (so at this stage we know that time needed to do the whole job will be less than 5 2-hour periods or 10 hours, as $$5*\frac{5}{24}=\frac{25}{24}>1$$).

Now in 8 hours (4 two hour periods) they do $$4*\frac{5}{24}=\frac{20}{24}$$th of the whole job. Then will be A's turn and by the end of 9 hours $$\frac{20}{24}+\frac{3}{24}=\frac{23}{24}$$th of the job will be done and $$\frac{1}{24}$$th will be left, which can be done by B (as it's B's turn now) in 1/2hours (30 minutes). So total time $$8+1+\frac{1}{2}=9\frac{1}{2}$$, hence they will finish at $$9:00AM+9\frac{1}{2}=18:30PM$$.

Similar problem: pipes-and-cisterns-93482.html#p719223

Hope it's clear.
_________________
Math Expert
Joined: 02 Sep 2009
Posts: 36567
Followers: 7081

Kudos [?]: 93212 [1] , given: 10553

Re: Working Alternately [#permalink]

### Show Tags

28 Jun 2010, 09:17
1
KUDOS
Expert's post
Thanks Bunuel for the detailed solution, can u pls advise why we calculated for 2 hrs?

2 hours is 1 cycle - a period of time when both A and B worked once. As long as we know what part of the job is done in one cycle we can find in which range to look for the correct answer. We had that the period of time must be less than 5 cycles (10 hours) and then we started calculating directly for 4 cycles, which saved us some time.
_________________
Intern
Joined: 12 May 2010
Posts: 22
Followers: 0

Kudos [?]: 1 [0], given: 0

Re: Working Alternately [#permalink]

### Show Tags

28 Jun 2010, 09:30
dont use the algebric way on this one. just draw a table and add the values: a=3/24 an b=2/24.
Manager
Joined: 24 Jan 2010
Posts: 164
Location: India
Schools: ISB
Followers: 2

Kudos [?]: 53 [0], given: 14

Re: Working Alternately [#permalink]

### Show Tags

28 Jun 2010, 09:34
Bunuel wrote:
Thanks Bunuel for the detailed solution, can u pls advise why we calculated for 2 hrs?

2 hours is 1 cycle - a period of time when both A and B worked once. As long as we know what part of the job is done in one cycle we can find in which range to look for the correct answer. We had that the period of time must be less than 5 cycles (10 hours) and then we started calculating directly for 4 cycles, which saved us some time.

Thanks Bunuel, One more question my understanding for "If they work together in stretches on 1 hr alternately," sentence was, they will work alternatively lets say A will work at 9:00 AM and B will start at 10:00AM. If my understanding is correct the how come 9th hr will come for A?
_________________

_________________
If you like my post, consider giving me a kudos. THANKS!

Manager
Joined: 24 Jan 2010
Posts: 164
Location: India
Schools: ISB
Followers: 2

Kudos [?]: 53 [0], given: 14

Re: Working Alternately [#permalink]

### Show Tags

28 Jun 2010, 09:36
mikioso wrote:
dont use the algebric way on this one. just draw a table and add the values: a=3/24 an b=2/24.

It will be helpful Mikioso, if u can explain that method.
_________________

_________________
If you like my post, consider giving me a kudos. THANKS!

Kaplan GMAT Instructor
Joined: 21 Jun 2010
Posts: 148
Location: Toronto
Followers: 44

Kudos [?]: 186 [0], given: 0

Re: Working Alternately [#permalink]

### Show Tags

28 Jun 2010, 09:37

Thanks Bunuel, One more question my understanding for "If they work together in stretches on 1 hr alternately," sentence was, they will work alternatively lets say A will work at 9:00 AM and B will start at 10:00AM. If my understanding is correct the how come 9th hr will come for A?

Hi,

A goes first, so A does the 1st hour, 3rd hour, 5th hour, 7th hour, 9th hour, ...
Manager
Joined: 24 Jan 2010
Posts: 164
Location: India
Schools: ISB
Followers: 2

Kudos [?]: 53 [0], given: 14

Re: Working Alternately [#permalink]

### Show Tags

28 Jun 2010, 09:40
skovinsky wrote:

Thanks Bunuel, One more question my understanding for "If they work together in stretches on 1 hr alternately," sentence was, they will work alternatively lets say A will work at 9:00 AM and B will start at 10:00AM. If my understanding is correct the how come 9th hr will come for A?

Hi,

A goes first, so A does the 1st hour, 3rd hour, 5th hour, 7th hour, 9th hour, ...

Thanks skovinsky, now I got it
_________________

_________________
If you like my post, consider giving me a kudos. THANKS!

Manager
Joined: 15 May 2009
Posts: 172
Followers: 4

Kudos [?]: 26 [0], given: 3

Re: Working Alternately [#permalink]

### Show Tags

30 Jun 2010, 09:00
mmm... the working alternately thing is kind of a pain.

So in the first hour A did 1/8th of the job, & in the 2nd hour B did 1/12th of the job. In 2 hours, they did 5/24 of the job together. Meaning in 8 hours they would have completed (5/24)X4=20/24.

In the 9th hour, A is on shift again & completes 1/8th (or in other words, 3/24th) of the job, so we're now that 23/24. In the 10th hour, B completes the remainder 1/24th. We know B can do 1/12th in 1 hour, so she'll only take half the hour to complete 1/24th of the job.

We do some counting with our fingers & see that it takes 9.5 hours. So starting at 0900 (9am in civilian time), we would complete the job at 18:30 or 6:30pm.

Kind of a pain in the ass but doable in 2 minutes.
Manager
Joined: 26 Feb 2012
Posts: 116
Location: India
Concentration: General Management, Finance
WE: Engineering (Telecommunications)
Followers: 0

Kudos [?]: 19 [0], given: 56

Re: Two women, A and B working separately can mow a field in 8 [#permalink]

### Show Tags

28 Jul 2013, 00:46
Two women, A and B working separately can mow a field in 8 and 12 hrs respectively. If they work together in stretches on 1 hr alternately, A beginning at 9:00 AM, when will the mowing be finished?

HI Bunnel
Please clarify me where I have gone wrong

Rate A-1/8
Rate B-1/12

let say A works for 4 hour and rate is 1/8 so total job done = 1/8*4=1/2
Similarly let say B works for 6 hour and rate is 1/12 so total job done=1/12*6=1/2

So both can finish the work in 10 hours if they work alternatively. 9.00 am+10 hour=19.00pm answer

Where i have gone wrong..............

Rgds
Prasannajeet
Math Expert
Joined: 02 Sep 2009
Posts: 36567
Followers: 7081

Kudos [?]: 93212 [0], given: 10553

Re: Two women, A and B working separately can mow a field in 8 [#permalink]

### Show Tags

28 Jul 2013, 04:01
prasannajeet wrote:
Two women, A and B working separately can mow a field in 8 and 12 hrs respectively. If they work together in stretches on 1 hr alternately, A beginning at 9:00 AM, when will the mowing be finished?

HI Bunnel
Please clarify me where I have gone wrong

Rate A-1/8
Rate B-1/12

let say A works for 4 hour and rate is 1/8 so total job done = 1/8*4=1/2
Similarly let say B works for 6 hour and rate is 1/12 so total job done=1/12*6=1/2

So both can finish the work in 10 hours if they work alternatively. 9.00 am+10 hour=19.00pm answer

Where i have gone wrong..............

Rgds
Prasannajeet

I think you misinterpreted the question. A and B work in shifts: A goes first and works for 1 hour, then goes B and works for 1 hour, ... Thus, for this scenario it's not possible A to work 4 hours and B 6 hours.
_________________
GMAT Club Legend
Joined: 09 Sep 2013
Posts: 13459
Followers: 575

Kudos [?]: 163 [0], given: 0

Re: Two women, A and B working separately can mow a field in 8 [#permalink]

### Show Tags

10 Aug 2014, 06:53
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
GMAT Club Legend
Joined: 09 Sep 2013
Posts: 13459
Followers: 575

Kudos [?]: 163 [0], given: 0

Re: Two women, A and B working separately can mow a field in 8 [#permalink]

### Show Tags

12 Oct 2015, 08:42
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
Manager
Joined: 23 Sep 2015
Posts: 96
Concentration: General Management, Finance
GMAT 1: 680 Q46 V38
GMAT 2: 690 Q47 V38
GPA: 3.5
Followers: 0

Kudos [?]: 14 [0], given: 213

Re: Two women, A and B working separately can mow a field in 8 [#permalink]

### Show Tags

09 Nov 2015, 13:37
Bunuel wrote:
prasannajeet wrote:
Two women, A and B working separately can mow a field in 8 and 12 hrs respectively. If they work together in stretches on 1 hr alternately, A beginning at 9:00 AM, when will the mowing be finished?

HI Bunnel
Please clarify me where I have gone wrong

Rate A-1/8
Rate B-1/12

let say A works for 4 hour and rate is 1/8 so total job done = 1/8*4=1/2
Similarly let say B works for 6 hour and rate is 1/12 so total job done=1/12*6=1/2

So both can finish the work in 10 hours if they work alternatively. 9.00 am+10 hour=19.00pm answer

Where i have gone wrong..............

Rgds
Prasannajeet

I think you misinterpreted the question. A and B work in shifts: A goes first and works for 1 hour, then goes B and works for 1 hour, ... Thus, for this scenario it's not possible A to work 4 hours and B 6 hours.

hey Bunuel,

thanks for the solution,

I just have one questions

if the rate came to 5/25 instead of 5/24, would the answer me 10 hours?

I stopped my solution at time = 24/5 = about 9.8 hours. Not sure what alerts us to solve further for the breakdown.
SVP
Joined: 17 Jul 2014
Posts: 2197
Location: United States (IL)
Concentration: Finance, Economics
Schools: Stanford '19 (S)
GMAT 1: 560 Q42 V26
GMAT 2: 550 Q39 V27
GMAT 3: 560 Q43 V24
GMAT 4: 650 Q49 V30
GPA: 3.92
WE: General Management (Transportation)
Followers: 20

Kudos [?]: 270 [0], given: 140

Re: Two women, A and B working separately can mow a field in 8 [#permalink]

### Show Tags

09 Nov 2015, 21:02
the answer should be 18:30
let's assume that the total work is 48
the A will do in 1 hour 6 parts of the work, B will do 4 parts of the work
2 hours - 10 parts of the work
4 hours - 20 parts
6 hours - 30 parts
8 hours - 40 parts
9 hours - 46 parts
9.5 hours - 48 parts

started at 9AM + 9.5hr = 18:30
Re: Two women, A and B working separately can mow a field in 8   [#permalink] 09 Nov 2015, 21:02
Similar topics Replies Last post
Similar
Topics:
How many different committees can be formed from a group of two women 4 10 Jun 2016, 00:01
6 A, B and C, each working alone can complete a job in 6, 8 and 12 days 10 15 Mar 2016, 11:32
12 At 8am on Thursday, two workers, A and B, each start working independe 6 04 May 2015, 04:42
2 Three boys, two girls, and two women are to be seated on a b 4 05 Feb 2014, 20:48
2 Two pipes A and B can fill a tank in 8 hours. If only pipe A is open 10 05 May 2010, 17:47
Display posts from previous: Sort by

# Two women, A and B working separately can mow a field in 8

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics

 Powered by phpBB © phpBB Group and phpBB SEO Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.